DESCRIPTION: In November, 1996 a workshop sponsored by NIOSH and the Association of Occupational and Environmental Clinics was convened to discuss solvent exposure in Railroad (RR) workers. Explicit questions were posed regarding the health effects of solvents, as well as recommended actions. The conference specifically suggested research utilizing functional imaging to determine the presence and severity of neuropathology following solvent exposure. Another area of interest was how to estimate the levels of past solvent exposure using a range of methods, such as interviews and modeling. This proposal incorporates both of these suggestions. We propose to assess central nervous system activation with Positron Emission Tomography (PET) in a sample of workers employed in the RR industry. Solvent exposure will be evaluated with a structured interview to ascertain an estimate of cumulative exposure. A battery of neuropsychological tests will be administered, as well as indices to assess psychiatric function. Exposed workers will be selected from a sample of over 180 workers who have been seen in the Occupational and Environmental Health Clinic at the West Virginia University School of Medicine. Workers have been exposed to solvents for at least 10 years and have been categorized by degree of exposure - mild, moderate, severe. A random sample of 16 workers from each category will be selected for inclusion in the protocol (N = 48). An equal number of nonexposed blue-collar control workers will be assessed with the same battery of tests and compared to the exposed subjects. We predict that exposed workers will show a pattern of brain activation that is significantly different from controls and specifically, involving a relatively diminished activation in the frontal cortex such that other cortical areas are recruited when subjects perform a memory task. In addition, there will be a dose-response relationship between exposure and neural activation.